OPTICAL GROUND SUPPORT EQUIPMENT (OGSE)
The ISO (Infrared Space Observatory) collimator is based on a Newton system with a parabolic primary mirror of 700 mm diameter and f/4 aperture and a plane secondary which tilts the beam by 90 degrees. The wavefront error at 550 nm is smaller than /25 RMS. The light sources are situated on the side of the tube and positioned by 3 crossed linear translation stages.
The tube of the collimator is supported by linear translation stages which allow tilting the collimator axis within a cone of 2 arcsec.
This device has been developed to qualify the optics of small size telescopes in the workshop.
This collimator is made of a parabolic mirror with a focal length of 2800 mm and a diameter equal to 350 mm.
The wavefront error is better than /50 at 550 nm.
The body of the collimator is a cylinder made of invar, supported by two XY motorized systems at each extremity.
These XY systems are controlled by micro-processor and allow, by combining their movements, to move the optical axis inside a 2° cone with accuracy equal to 1 arcsecond. The stability of the structure was a major parameter. The optical axis has stability with respect to the base structure better than 1 milliarcsecond.
This collimator is certified to work under 10-6 mbar vacuum. It was developed to meet the specifications of CSL and MATRA for the alignment of the HIPPARCOS (HIgh Precision PARallax COllecting Satellite) payload.
The equipment is part of the Optical Ground Support Equipment of the HELIOS satellite. The following items have been delivered:
• Motorized support collimator
• 4 axes mounting for an aspheric mirror (ø 700 mm)
• 2 axes mounting for a flat mirror (diameter 400 mm).
All motions are computer-controlled. The accuracy of the angular positioning is 0.4 arcsec. The testing bench and calibration have been performed by AMOS.
Structural (static, dynamic) and thermal analyses were necessary because of the very tight specifications concerning mechanical and thermal stabilities.
These mounts are class 100 and vacuum ( 10-6 mbar) compatible.
AMOS was responsible for the study and the manufacturing of the SILEX (Semiconductor Intersatellite Link EXperiment) telescope.
The main structure of the telescope consists of a cylinder made of stainless steel material. The supports of the primary and secondary mirrors are insensitive to thermal variations. The alignment of the secondary mirror with the optical axis of the primary mirror is performed with the available motions on the spider and on the secondary mirror itself.
The inner wall of the cylinder as well as the mirror supports and baffles are black painted (vacuum compatible) to reduce the surface scattering.
The telescope has an optical quality better than /40 RMS WFE at 633 nm.
This collimator was designed and manufactured following the specifications of SPACEBEL INSTRUMENTATION and MATRA.
Meteosat second Generation (SEVIRI)
The aim of this OGSE instrument was to deliver some optical stimuli to SEVIRI (Spinning Enhanced Visible and IR Imager telescope) for testing its main performances. The instrument was used in vacuum (10-6 mbar) to perform :
geometric measurements (MTF and coregistration of SEVIRI) in dynamic and static configurations (the instrument generates stimuli in similar conditions to the real value seen by SEVIRI) ;
radiometric measurements (to perform the calibration of SEVIRI) ;
polarisation measurements (measure of radiometric sensitivity to polarisation of SEVIRI).
The function of the collimator is to display in front of MERIS (MEdium Resolution Imaging Spectrograph) a polychromatic reference line for the purpose of spectral registration and MTF measurement tests.
The instrument is used under vacuum (10-6 mbar) and it is designed around a Newton on-axis optical configuration with a primary mirror diameter equal to 250 mm.
XMM vertical testing facility
The XMM satellite
The XMM (X-Ray Multi-Mirror Mission) satellite included three grazing incidence telescopes (called Mirror Modules or MM) of the Wolter 1 type, designed to work in the X-ray zone of the 0.1-10 keV with a focal length of 7.5 metres.
Vertical testing facility
AMOS has designed and manufactured the vertical mirror test facility of the European satellite XMM on behalf of CSL. This installation is situated in a building which includes offices, meeting rooms, work shops, a clean room, a cellar and a pit (11 metres in depth).
The mirrors are inserted into Focal X (the name of the space simulator) with the help of a robotic manipulator, and placed on the mechanisms which lie on an optical bench. EUV and X-ray beams are then produced with the help of the light sources situated in the pit 11 metres lower down and sent towards the mirrors. They then reflect the beams towards the detectors situated 7.5 metres above a tower that is fixed on the optical bench. The mechanisms that are situated on the optical bench and above the tower enable the various test configurations to be carried out. The optical bench and the tower are supported by three legs fixed on a seismic block, lying on elastomer blocks so as to isolate the whole assembly from ground vibrations. The tower can be inclined to an angle varying from - 2° to + 7.5°.
All the mechanisms are entirely automated and remotely controlled. The lower mechanisms enable two translations, one rotation and two tilts of the specimen (XMM mirrors). The upper mechanisms allow three translations and two rotations in order to move the two X-Ray detectors and the EUV detector. The inclination of the tower, the two translations of the manipulator and the opening/closing of the two lateral doors (2,5 metres diameter) are also automated.
- Operational temperature : 20 ± 2°C
- Vacuum limit : 10-6 mbar
- Leak rate : 10-3 mbar l/s
- Molecular cleaning : < 2 10-8 g/cm2
- First eigen frequency of the tower : 14.5 Hz
- Number of automated axes : 19
- Translation measuring resolution : 1 micron
- Rotation measuring resolution : 2,5 arcsec
- Repeatability : ± 10 microns
Optical performance (EUV collimator)
- Micro-roughness of the mirrors : < 10 Å RMS
- Optical quality of the primary mirror : < 42 nm RMS Wave Front Error
- Optical quality of the secondary mirror : < 33 nm RMS Wave Front Error
- Image quality : < 63 nm RMS Wave Front Error
4 motorized axes collimator (2 translations and 2 rotations) which is able to map the field of view of the IASI instrument (Fourier Transform Infrared Spectrometer):
• Wavefront quality 150 nanometers RMS
• Pointing accuracy better than 100 rad
• Axis stability better than 10 rad
• Collimation quality better than 10 km
This collimator is used under vacuum at Alcatel Alenia Space (France).
One meter collimator for ISRO
AMOS has designed, manufactured, assembled, and aligned an integrated collimator provided to ISRO/SAC in India. The collimator is an F/15 folded Cassegrain combination with a 1m diameter fast parabolic primary mirror, and a fast hyperbolic secondary mirror. Each mirror is specified to present lambda/60 rms surface accuracy, and the MTF specification for the integrated collimator is highly demanding in terms of alignment. Moreover, the mechanical structure and mirror cells are designed to withstand gravity effects and a thermal variation of 10°C without loss of optical performance.
PLANCK Primary Reflector Test Equipment
AMOS designed and fabricated for CSL a spherical convex mirror of 1,5m diameter in aluminium alloy 5083 and integrated it on a 4 axis support.
This mirror is used as an autocollimating element in the qualification test of the Primary Reflector of PLANCK.
(PLANCK is an ESA satellite dedicated to the measurement of the universe cosmic background).
It is used at cryogenic temperature (10 K) and its position is adjustable in focus and tip-tilt with a resolution of 1 micron through a programmable logic controller.
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